Volume 135, 2018, pp. 572–582 DOI: 10.1642/AUK-17-224.1 RESEARCH ARTICLE Classic pattern of leapfrog migration in Sooty (Passerella iliaca unalaschcensis) is not supported by direct migration tracking of individual

Kevin C. Fraser,1*Amelie´ Roberto-Charron,1 Bruce Cousens,2 Michael Simmons,3 Ann Nightingale,3 Amanda C. Shave,1 Renee´ L. Cormier,4 and Diana L. Humple4

1 Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba, Canada 2 Georgia Basin Ecological Assessment and Restoration Society, Nanaimo, British Columbia, Canada 3 Rocky Point Observatory, Victoria, British Columbia, Canada 4 Point Blue Conservation Science, Petaluma, , USA * Corresponding author: [email protected] Submitted November 22, 2017; Accepted February 22, 2018; Published May 9, 2018

ABSTRACT Leapfrog migration systems, whereby more-northern breeding populations overwinter the farthest south, provide unique opportunities to further our understanding of how environmental variation shapes migratory behavior and the seasonal distributions of birds. Leapfrog migration in a western Fox Sparrow subspecies complex (Passerella iliaca unalaschcensis, ) was described as early as 1920, and has served as an exemplar of leapfrog systems in subsequent theoretical work. However, migration behavior within P. i. unalaschcensis has never been studied directly, nor has the proposed leapfrog pattern been confirmed through the tracking of individuals. Using light-level geolocators and GPS tags, we tested the long-standing pattern of leapfrog migration in Sooty Fox Sparrows by determining spatiotemporal movement patterns for individuals originating from a northern (Vancouver Island, British Columbia) and a more southern (Point Reyes, California) overwintering region, where migratory timing, routes, and breeding locations were predicted to differ. Our results did not support the proposed leapfrog migration pattern in several ways. Individuals overwintering on Vancouver Island were predicted to be sedentary and/or breed locally, but we found they traveled more than 3,000 km to breeding sites in coastal northwestern British Columbia and southern Alaska. Birds overwintering in California had breeding locations that overlapped those of birds from British Columbia, as well as the predicted breeding regions of 4 other subspecies. Lastly, spring and fall migration routes were largely coastal for both groups, and we found no evidence of a proposed transoceanic fall migration route between Alaskan breeding sites and Californian overwintering sites. Thus, our results do not support the long-held pattern of leapfrog migration in Sooty Fox Sparrows and further highlight that bio-logging tools can reveal important new insights into patterns of migratory behavior, even in relatively well-studied systems. Keywords: bio-logging, geolocator, migration ecology, migratory connectivity, movement ecology, songbird

Le patron classique de migration en saute-mouton chez Passerella iliaca unalaschcensis n’est pas appuye´ par le suivi de la migration directe des oiseaux RESUM´ E´ Les systemes` de migration en saute-mouton, selon lesquels les populations nichant le plus au nord passent l’hiver le plus au sud, fournissent des occasions uniques de mieux comprendre comment la variation environnementale fa¸conne le comportement migrateur et les distributions saisonnieres` des oiseaux. La migration en saute-mouton chez Passerella iliaca unalaschcensis (complexe de sous-especes` de l’Ouest de P. iliaca)aet´ ed´ ecrite´ des` 1920 et a servi d’exemple de systemes` de saute-mouton dans les travaux theoriques´ subsequents.´ Toutefois, le comportement de migration au sein de P. i. unalaschcensis n’a jamais et´ e´ etudi´ e´ directement et le patron de saute-mouton propose´ n’a pas et´ e´ confirme´ par le suivi d’individus. A` l’aide de geolocalisateurs´ legers´ et de balises GPS, nous avons teste´ le modele` etabli´ de longue date de la migration en saute-mouton chez P. iliaca unalaschcensis en determinant´ les patrons de deplacement´ spatio-temporels des individus provenant de regions´ d’hivernage nordiques (ˆıle de Vancouver, en Colombie- Britannique) et plus meridionales´ (Point Reyes, en Californie), ouonpr` edisait´ des differences´ dans la periode´ de migration, les voies migratoires et les aires de reproduction. Nos resultats´ n’appuyaient pas le patron de migration en saute-mouton propose´ de plusieurs fa¸cons. Nous avions predit´ que les individus qui hivernaient sur l’ˆıle de Vancouver etaient´ sedentaires´ et/ou se reproduisaient localement, mais nous avons trouve´ qu’ils se depla¸´ caient sur plus de 3 000 km jusqu’aux aires de reproduction sur les cotesˆ du nord-ouest de la Colombie-Britannique et du sud de l’Alaska. Les oiseaux qui hivernaient en Californie avaient des aires de reproduction qui chevauchaient celles des oiseaux de

Q 2018 American Ornithological Society. ISSN 0004-8038, electronic ISSN 1938-4254 Direct all requests to reproduce journal content to the AOS Publications Office at [email protected] K. C. Fraser, A. Roberto-Charron, B. Cousens, et al. No leapfrog migration in Sooty Fox Sparrow 573

Colombie-Britannique, de memeˆ que les regions´ de reproduction predites´ de quatre sous-especes.` Enfin, les routes migratoires au printemps et a` l’automne passaient principalement le long des cotesˆ pour les deux groupes et nous n’avons trouve´ aucune preuve d’une voie migratoire transoceanique´ en automne entre les sites de reproduction en Alaska et les sites d’hivernage en Californie. Ainsi, nos resultats´ n’appuient pas le modele` etabli´ depuis longtemps de la migration en saute-mouton chez P. i. unalaschcensis et soulignent davantage que les outils de bio-logging jeter un important nouvel eclairage´ sur les patrons de comportements migratoires, memeˆ dans des systemes` relativement bien etudi´ es.´ Mots-cles:´ ecologie´ de la migration, ecologie´ des deplacements,´ bio-logging, oiseau chanteur, geolocalisateur,´ connectivite´ migratoire

INTRODUCTION The Fox Sparrow (Passerella iliaca) is one of the most widely distributed migratory , with a breeding The spatiotemporal patterns of long-distance songbird range that spans continental . Owing to migration have fascinated generations of researchers great geographic variation in plumage, structure, and and provide important test beds for investigating the behavior, up to 18 subspecies of Fox Sparrow have been evolution of seasonal distributions and migration proposed (Weckstein et al. 2002), with 4 officially behavior. Intraspecific variation in migration timing, recognized (American Ornithologists’ Union 1998). Ge- routes, and seasonal distributions may arise through netic (mtDNA) evidence supports P. i. unalaschcensis competition, variation in the degree of seasonality, and/ (Sooty Fox Sparrow) as one of the 4 recognized North or habitat quality across species’ ranges (Newton 2008). American subspecies (Zink 1994). Sooty Fox Sparrow has Leapfrog migration is one such intraspecific pattern that been further divided into 6 or 7 subspecies, based upon has been reported in a diverse array of avian taxa in both morphological and plumage characteristics (Swarth 1920, New and Old World migration systems (Newton 2008). Webster 1983, Rising 1996, Weckstein et al. 2002). A In a leapfrog system, the most-northern breeding leapfrog migration system was described for the Sooty populations within a species have the longest migration group (Swarth 1920), and this system has since served as distance and overwinter the farthest south, leapfrogging an ‘‘exemplar’’ of leapfrog migration in numerous theoret- over more-southern breeders and their overwintering ical works as well as textbooks devoted to migration regions. Several hypotheses for the evolution of leapfrog ecology and behavior (Bell 1997, Alerstam and migration systems have been proposed. This pattern may Hedenstrom 1998, Newton 2008, Alcock 2009). Sooty Fox arise through competitive interactions, such as when Sparrows breed from the Canada–United States border to more-northern breeding individuals encounter non- the Alaskan Peninsula and winter from southern British breeding areas already occupied by more-southern Columbia to southern California (Weckstein et al. 2002). breeders that completed breeding earlier, and therefore Fox Sparrows overwintering in the southern British journey farther to acquire available sites (Newton 2008). Columbia region were ascribed to the P. i. fuliginosa Alternatively, this pattern may be driven by variation in subspecies of Sooty Fox Sparrow, and were described as habitat quality and/or seasonality at overwintering areas, ‘‘hardly migratory at all’’ with the exception of altitudinal or where higher-quality habitats may support longer local movements (Swarth 1920). Sooty Fox Sparrows migration distances, allowing birds that overwinter overwintering in California were expected to be the most farther south to leapfrog over more-southern breeders migratory and to leapfrog the more sedentary northern to sites farther north (Bell 1997); this was recently groups as they journeyed to and from breeding sites suggested for leapfrog migration in Wood Thrushes distributed across coastal areas of northwestern British (Hylocichla mustelina; McKinnon et al. 2015). New Columbia and southern Alaska (Swarth 1920). Within direct-tracking technologies now offer additional means these Californian overwintering subspecies, an east-to- of addressing critical knowledge gaps in our under- west partitioning of northern breeding regions was standing of migration patterns. They have recently been proposed, with the more southern overwintering subspe- used to confirm and elucidate transoceanic flights in cies (P. i. unalaschcensis, P. i. insularis, and P. i. sinuosa) Blackpoll Warblers (Setophaga striata;Delucaetal. journeying to breeding sites the farthest west (i.e. the 2015) and Connecticut Warblers (Oporornis agilis; greatest distance from overwintering sites), and a more McKinnon et al. 2017) and revealed within-winter northern overwintering subspecies (P. i. annectens) breed- movements of Swainson’s Thrushes (Catharus ustulatus; ing farther east (Swarth 1920, Bell 1997; Appendix Figure Cormier et al. 2013). Direct-tracking methods also 3). However, despite the large amount of morphological provide opportunities to investigate leapfrog migration and plumage variation used to distinguish the spatial patterns, but have only had limited application to date distribution of the different subspecies of Sooty Fox (McKinnon et al. 2013, 2015; Ramos et al. 2015). Sparrow, there is considerable overlap in these characters

The Auk: Ornithological Advances 135:572–582, Q 2018 American Ornithological Society 574 No leapfrog migration in Sooty Fox Sparrow K. C. Fraser, A. Roberto-Charron, B. Cousens, et al. between subspecies (Bent 1968, Pyle and Howell 1997), Vancouver Island, British Columbia, Canada: In 2013, complicating identification in the field and limiting the we deployed 30 MK20 light-level geolocators (no light ability to assess migration behavior and timing from stalk; 1.1 g; British Antarctic Survey) at several locations observational data. Thus, there has been a general lack of and private residences on southern Vancouver Island evidence of migration timing or routes to support the (around Victoria and Nanaimo; Appendix Table 1). For proposed leapfrog system. Further, Bell (1997) speculated stalkless geolocators, we trimmed contour feathers posi- that some subspecies overwintering in California may tioned directly over the light sensor to reduce shading embark on a fall transoceanic flight, a proposal that has not effects. The average weight of individual Fox Sparrows was been tested. New bio-logging technologies offer new 39.9 g, thus the total weight of the geolocator with harness opportunities to track the movement of individual Sooty (~0.1 g) averaged ,3.01% of the body weight. Point Reyes, Fox Sparrows, to empirically test these proposed patterns California, USA: In winter 2014–2015, we attached 22 for the first time. P65B114 light-level geolocators (14 mm stalks; Migrate Our objective was to use migratory-connectivity data Technology Ltd., Cambridge, UK; December 8, 2014, to collected from new bio-logging methods to test the long- February 11, 2015) and 15 Pinpoint-8 GPS tags (Lotek established pattern of leapfrog migration proposed for Wireless, Newmarket, Ontario, Canada; January 22 to subspecies of Sooty Fox Sparrow. We used archival light- March 9, 2015) to Fox Sparrows captured at constant level geolocators and GPS tags to track the movements of effort mist-netting stations or with Potter traps. Study sites Sooty Fox Sparrows originating from 2 widely separated included Point Blue Conservation Science’s Palomarin overwintering regions separated by approximately 1,200 Field Station in Point Reyes National Seashore, Pine Gulch km: southern Vancouver Island, British Columbia, and Creek in the Bolinas Lagoon Open Space Preserve, and one Point Reyes, California. Within the context of the site on private property in Bolinas (Appendix Table 1). In leapfrog migration system proposed by Swarth (1920), February 2016 we deployed an additional 2 light-level and later elaborated by Bell (1997) and others, we geolocators at Pine Gulch Creek. We attached the tags to predicted that individuals overwintering in the more Fox Sparrows with a leg-loop harness (Rappole and Tipton northern region (southwest British Columbia), where the 1991) of 1.0 mm cord (Stretch Magic jewelry cord; species occurs year-round, would have little to no annual Pepperell Braiding Co., Pepperell, Massachusetts, USA), movement, breeding locally or regionally, whereas birds closed with a metal crimp bead and sealed with super glue. from purely overwintering sites in California would The mean weight of Fox Sparrows tagged in the Point journey northward to breeding areas along the Alaska– Reyes area was 34.1 g, mean light-level geolocator tag British Columbia coast (Swarth 1920). This would follow weight with harness was ~1.0 g (,3% of mean weight), a pattern Bell (1997) ascribed to varying seasonality and and mean weight GPS tag with harness was 1.3 g (,4% of patterns of food abundance across the overwintering mean weight); while all individuals were eligible for the range. Further, we evaluated whether the California lighter light-level tags, we only considered birds .29 g for wintering birds made a transoceanic fall journey back to a GPS tag (and .31 g for the heaviest tags). their overwintering sites (Bell 1997) or if they took a A tail feather (British Columbia) or 8–10 contour coastal route. feathers (California) were collected from each geolocator- tagged Fox Sparrow and stored for later genetic (sexing) METHODS analysis by commercial laboratories: HealthGene (Toronto, Ontario, Canada) for British Columbia birds, and Animal Data Collection Genetics Inc. (Tallahassee, Florida, USA) for birds from We captured Sooty Fox Sparrows in late winter (Jan–Mar California. 2013 in British Columbia; Dec–Feb 2014–2015 and Feb 2016 in California) using Potter traps or mist nets and Geolocator Data Analysis banded, measured, and aged them on the basis of skull Light-level geolocators (hereafter ‘‘geolocators’’) record ossification, rectrix shape, and/or plumage characteristics time and light levels, which we used to determine (Pyle and Howell 1997) as first-winter immature (HY/SY) geographic coordinates based on solar noon and the or after-hatch-year adult (AHY/ASY) and fitted them with length of the day (Hill and Braun 2001). Twilight times a light-level geolocator or an archival GPS unit and one or were identified using the BAStag package (Wotherspoon et two color bands. The following winters, tag recovery al. 2013) in R (R Core Team 2017), using the threshold occurred passively at constant effort mist-netting stations, method (Lisovski et al. 2012) with a threshold of 1.5 or actively for returned birds using Potter traps or target (Cooper et al. 2017). The data were visually inspected and nets; when banded birds were recaptured, the data logger, twilight errors (false sunrises or sunsets owing to shading harness, and color band were removed, and the data were of the light sensor or other light interference) were downloaded for analysis. removed. We then analyzed the data in a Bayesian

The Auk: Ornithological Advances 135:572–582, Q 2018 American Ornithological Society K. C. Fraser, A. Roberto-Charron, B. Cousens, et al. No leapfrog migration in Sooty Fox Sparrow 575 framework in the Satellite Geolocation for Animal estimated migration distance by measuring the shortest Tracking (SGAT) package (Wotherspoon et al. 2013) in distance between stationary positions (stopovers) using R, which uses Markov Chain Monte Carlo (MCMC) ArcGIS. simulations to determine movements with appropriate confidence intervals fit to estimate animal locations while Identification of Breeding Sites incorporating location error (Sumner et al. 2009). We Using geolocator data, arrival at the breeding site was followed the methods outlined by Cooper et al. (2017) and identified by the changeLight and mergeSites functions provided the model with (1) raw location coordinates from the GeoLight package in R (Lisovski and Hahn 2013). derived from the threshold method, (2) a model describing We used the stationary sites summary function to provide the error in twilight times, (3) a spatial mask outlining breeding site location estimates. As 95% credible intervals probable positions for the species, and (4) behavioral are not provided by this package, we calculated these by model defining possible and likely flight speeds. averaging the coordinates and credible intervals from the We calibrated data using a distribution of values SGAT results during the known time period that the calculated for each bird while it was at a known location individual was on the breeding grounds. GPS units were (the deployment location). We determined an appropriate programmed to collect a spatial point every 10 days during zenith angle (marking the angle of the sun in relation to the breeding period, beginning June 1, for up to 10 points the known location, when light levels cross the 1.5 before battery life was depleted. threshold) to account for any environmental interference in light levels that may impact what is measured by the RESULTS light sensor of the geolocator. To estimate locations using SGAT, for each tag (bird) we used 3 independent Markov We retrieved 10 geolocators at field locations in Nanaimo chains to draw 120,000 estimated locations for burning in (n ¼ 3) and Victoria (n ¼ 7), British Columbia (BC), after and tuning the model. A final 15,000 estimated locations birds returned to their overwintering sites (Oct–Mar); one were used to identify the posterior distribution (Cooper et geolocator (deployed at Victoria) did not provide useable al. 2017). The behavioral model and spatial mask helped data due to strong shading of the light sensor. In total 16 of constrain the estimates and remove unrealistic results 30 (53.3%) geolocator-carrying birds returned to the during the equinox. The land mask was defined to make deployment sites in BC. We retrieved 3 geolocators and 5 positions on land 5 times more likely than those on water. GPS tags from Point Reyes, California (CA), in 2015–2016 This mask was extended to permit locations from shore to (Oct–Feb) and none in winter 2016–2017; 2 of the GPS 500 km offshore (but positions still 5 times more likely tags failed to collect any data and the remaining 3 collected over land), and constrained multiple-day travel over water. 1–3 locations each (Appendix Table 1). All individuals We also ran the model without the land mask for each bird tracked from the British Columbia overwintering popula- for comparison. The behavioral model was a function used tion (n ¼ 9) went to breeding locations in northwestern in the analysis and was framed in terms of expected British Columbia or southern Alaska and individuals maximum flight speeds, with higher probability assigned to tracked using geolocators (n ¼ 3) or GPS tags (n ¼ 3) travel speeds under 60 km hr1. While framed in terms of from the Point Reyes, California, overwintering location flight speed, this also resulted in short-distance move- also went to the same region (Figure 1, Appendix Figure 4). ments being more likely, and long-distance movements The 3 GPS-tagged birds from California whose exact less likely. This served to discard unrealistic latitudinal breeding-season locations (,10 m) could be determined estimates that can be caused (for example) by shading of traveled to coastal areas in the Gulf of Alaska, from the light data and during the equinoxes. Some uncertainty Wrangell-Saint Elias National Park and Preserve to as far remained in the latitudinal estimates during the equinox west as Kodiak Island, and those carrying geolocator tags and therefore up to 2 weeks of coordinates on either side bred at nearby sites to the east. of the equinox were discarded. Spring migration routes were largely coastal for both groups (BC n ¼ 4, CA n ¼ 3; Figure 2). Fall migration Identification of Stopover Sites and Migration Timing routes for Point Reyes geolocator-tagged individuals were Using Geolocators also coastal and not transoceanic (n ¼ 3; Figure 2). Results The changeLight and mergeSites functions from the showed a coastal route with or without the land mask package GeoLight were used to determine stationary and applied during the SGAT analysis. Due to extensive movement periods (Lisovski and Hahn 2013), allowing us plumage/habitat shading of the stalkless light sensor and to determine stopover locations and the timing of subsequent location error, we were not able to determine migration. Due to their overlap in timing with the spring fall migration routes for birds from the BC group. The and autumnal equinox, departure from the wintering sites timing of breeding arrival date for the southern (CA) and and breeding sites could not reliably be determined. We more northern (BC) overwintering sites did not differ (t ¼

The Auk: Ornithological Advances 135:572–582, Q 2018 American Ornithological Society 576 No leapfrog migration in Sooty Fox Sparrow K. C. Fraser, A. Roberto-Charron, B. Cousens, et al.

of mixing of individuals from the 2 wintering areas across the breeding grounds that does not support the leapfrog pattern. Individuals we tracked from a single, southern nonbreeding region (Point Reyes, California) had a breeding distribution spanning the predicted distributions of up to 4 subspecies overwintering in California, while those tracked from the 2 northern wintering sites ,100 km apart (Victoria and Nanaimo, British Columbia) spanned the proposed breeding ranges of 5 subspecies. We also found no evidence of a great circle route during fall migration for birds overwintering in California, in which birds were predicted to make a transoceanic flight from Alaska to California in fall (Bell 1997). Rather, individuals tracked from California took a coastal or inland route in both fall and spring and did not make an open- ocean crossing during fall migration. However, while our analysis suggests a fall coastal route is most likely, credible intervals did overlap with open ocean in some cases so further tracking is required to confirm a fall coastal route. According to Swarth’s (1920) geographical range delin- eation that was elaborated by Bell (1997), the Fox Sparrow individuals we encountered and tracked from overwinter- ing sites on Vancouver Island would be expected to be P. i. fuliginosa. Swarth (1920) notes that Sooty Fox Sparrow of the fuliginosa type overwintering in southern British FIGURE 1. Breeding locations of Sooty Fox Sparrows tracked Columbia ‘‘. . .hardly migrates at all’’ and may be an using archival light-level geolocators and GPS tags from 2 overwintering regions (Vancouver Island, British Columbia; Point altitudinal migrant. This inference seems to be based upon Reyes, California). Deployment locations are indicated by black observations that Sooty Fox Sparrows overwintering on symbols. Vancouver Island and region depart these locations in spring, and that breeding birds of similar plumage 1.2014, df ¼ 2.8435, P ¼ 0.32) and ranged from April 25 to characteristics were observed at high elevation on nearby May 28. Spring migration distance for the BC group was coastal islands in Puget Sound (Dawson 1909). Swarth 3,300–3,700 km. Spring distance for CA birds was 2,800– seems to thereby infer that birds departing low-elevation 2,900 km and fall distance was 2,700–3,500 km. Based overwintering sites are the same individuals observed upon the genetic sexing analysis, 2 of the 10 BC individuals breeding locally at higher elevation on coastal islands were female (the sex of the remainder could not be (Dawson 1909). Swarth also collected specimens he identified with the analysis) and 3 of the 6 CA birds determined to be fuliginosa on Vancouver Island during tracked were female and the other 3 were male. the breeding season (Swarth 1920). Our measurements and visual assessment of individuals captured and tracked DISCUSSION on Vancouver Island were consistent with the subspecies P. i. fuliginosa but also overlapped with the measurements for Despite the long-standing description of leapfrog migra- other subspecies within the Sooty Fox Sparrow group that tion within the west coast Sooty Fox Sparrow group may also overwinter in this area (Pyle and Howell 1997). (Swarth 1920) and subsequent theoretical work (Bell Nevertheless, our results do show that the individuals we 1997), we did not find evidence supporting this pattern encountered overwintering in the region Swarth ascribed based upon our direct tracking of individuals from 2 to P. i. fuliginosa were not relatively sedentary nor engaged disjunct overwintering regions (British Columbia and only in altitudinal migration to local breeding sites, California) predicted to differ in their breeding locations. although it is unknown if patterns may differ from those Instead, we found that birds expected to be more sedentary of a century ago. Clearly, our results suggest further work (British Columbia) engaged in long-distance spring on the movement ecology of Sooty Fox Sparrows migration of greater than 3,000 km to reach breeding sites overwintering in this region is required to further elucidate in northwestern British Columbia and throughout coastal these patterns, including the tracking of birds that breed southern Alaska. Further, we found an unexpected degree locally in the region.

The Auk: Ornithological Advances 135:572–582, Q 2018 American Ornithological Society K. C. Fraser, A. Roberto-Charron, B. Cousens, et al. No leapfrog migration in Sooty Fox Sparrow 577

FIGURE 2. Spring and fall migratory routes for individual Sooty Fox Sparrows tracked by using archival light-level geolocators from 2 overwintering regions (Vancouver Island, British Columbia; Point Reyes, California). (A) Inset map of breeding and overwintering region; (B–E) spring migration routes for birds tracked from British Columbia; (F–H) spring and fall migration routes for birds tracked from California. Red dashed lines: spring routes; blue dashed lines: fall routes. Black bars show 95% credible intervals for migratory stopover locations. Far inland routes for 3 birds tracked from British Columbia (B, C, E) crossing the Coast Range Mountains are likely an artefact of shading bias of geolocators without a light stalk, causing a northward shift in position; these routes are also expected to be coastal.

The Auk: Ornithological Advances 135:572–582, Q 2018 American Ornithological Society 578 No leapfrog migration in Sooty Fox Sparrow K. C. Fraser, A. Roberto-Charron, B. Cousens, et al.

A pattern of strong connectivity was proposed for uals in an overwintering population share a distinct subspecies of Sooty Fox Sparrow overwintering in breeding range that is largely nonoverlapping with other California (Swarth 1920, Bell 1997). In this system, a populations. While we do not have the breadth of data west-to-east breeding distribution in coastal Alaska to required to quantify migratory connectivity (Ambrosini et northwestern British Columbia was predicted for subspe- al. 2009), our results suggest a weak pattern of connectiv- cies (unalaschcensis, insularis, sinuosa, and annectens) that ity, due to the mixing of overwintering groups at breeding winter in California. The proposed overwintering range for sites that we have documented by using direct tracking. P. i. annectens overlaps with our Point Reyes study area Furthering our understanding of migratory connectivity but, as with individuals captured on Vancouver Island, patterns in Sooty Fox Sparrows would not only further overlap in morphometrics and plumage characteristics elucidate spatial distributions of subspecies in this group, precluded us from successfully ascribing tagged individuals but would also be invaluable for identifying areas for future in California to a subspecies within the Sooty Fox Sparrow conservation and management of Fox Sparrows across the group. Within the proposed leapfrog system, birds north-Pacific coast, particularly considering a 4.08% yr1 originating from this overwintering location were predict- decline documented in the Pacific Northwest through the ed to breed along the coast of southeastern Alaska and Breeding Bird Survey (Sauer et al. 2017). northwestern British Columbia (Swarth 1920, Bell 1997). Differential migration between sexes and age classes has In contrast, our results show that individuals tracked from been described in some other sparrows that breed in North Point Reyes had breeding locations that span all of coastal America, but it remains unclear whether these patterns southern Alaska, and overlap with the predicted breeding exist for western-breeding Fox Sparrows. Since Fox distributions of other supposed California-wintering sub- Sparrows are sexually monomorphic, we attempted to species, as well as those wintering in Oregon, , determine sex genetically from feather DNA analysis. The and British Columbia (Swarth 1920, Bell 1997). Thus, these males and females tracked from the same Californian results are also not consistent with the spatial partitioning overwintering locations traveled similar distances to an of breeding locations required within the framework of the overlapping breeding area in Alaska. The 2 females tracked proposed leapfrog system. from overwintering locations in British Columbia traveled Bell (1997) proposed a ‘‘trans-oceanic great circle route’’ more than 3,000 km to a breeding region that overlapped for Fox Sparrow groups overwintering in California, where with other individuals tracked from the same locations. birds use a northward coastal route in spring and make a These preliminary results suggest that coastal-breeding large, open-ocean crossing from Alaska to California in western Fox Sparrows are not differential migrants. fall, utilizing favorable wind patterns. However, the 3 fall However, we recommend that future research target the tracks we obtained for birds journeying between Alaska investigation of partial migration in this system, particu- and California show routes that are inland or coastal. As larly now that we have identified that birds anticipated to further direct confirmation, observation and photo docu- be relatively sedentary year-round in southern BC migrate mentation of a fallout of nocturnal songbird migrants on a great distances. cruise ship near land approaching Ketchikan, Alaska, on While our data do not support the leapfrog system first September 29, 2017, included Sooty Fox Sparrows (Skei proposed by Swarth (1920) and much explicated by 2017). Thus we did not find any evidence to support a subsequent works, the reasons for the mismatch are not transoceanic fall route, such as has been described recently clear. Recent evidence shows that migration systems can for other migratory songbirds journeying to overwintering undergo rapid changes, with migration behavior being sites in fall (DeLuca et al. 2015, McKinnon et al. 2017). quickly lost, or substantially altered, on a decadal scale Further direct tracking of subspecies overwintering in when favored by local conditions (e.g., Bearhop et al. 2005, California, or those breeding in the western portion of Winkler et al. 2017). Further, overlapping or shifting south coastal Alaska, could determine if such an open- seasonal distributions at a fine scale of groups with ocean fall route is taken by any Sooty Fox Sparrows. different movement or connectivity patterns can be Patterns of migratory connectivity, or the strength of difficult to discern (Nelson et al. 2016). Thus, it remains connection between breeding and nonbreeding popula- unclear whether the leapfrog system in Sooty Fox tions, can be important to informing our understanding of Sparrows was inaccurately characterized initially, or if factors driving the seasonal distributions of populations there has been a subsequent shift in migration behavior and of factors shaping population dynamics (Webster et al. and distribution since it was first described in 1920. We 2002). While work by Swarth (1920) and Bell (1997) hope that this initial exploration by using direct-tracking predates the terminology and a recent substantial litera- methods inspires further research on the structure of this ture on migratory connectivity (McKinnon et al. 2013), the fascinating migratory system and the many others where leapfrog migration system they proposed could be critical gaps in our understanding of spatiotemporal described as reflecting strong connectivity, where individ- patterns remain.

The Auk: Ornithological Advances 135:572–582, Q 2018 American Ornithological Society K. C. Fraser, A. Roberto-Charron, B. Cousens, et al. No leapfrog migration in Sooty Fox Sparrow 579

ACKNOWLEDGMENTS Assortative mating as a mechanism for rapid evolution of a migratory divide. Science 310:502–504. We thank Emily McKinnon for organizing the symposium Bent, A. (1968). Life Histories of North American Cardinals, ‘‘Best tools for studies of small landbird movements in the Grosbeaks, Buntings, Towhees, Finches, Sparrows, and Allies. golden age of bio-logging’’ at the 135th meeting of the Smithsonian Institution, Washington, DC, USA. American Ornithological Society and for the invitation to Cooper, N. W., M. T. Hallworth, and P. P. Marra (2017). Light-level contribute to this special issue of The Auk devoted to new geolocation reveals wintering distribution, migration routes, discoveries by using direct-tracking methods. We thank James and primary stopover locations of an endangered long- Fox and Migrate Technology Ltd. and Lotek Wireless Inc. for distance migratory songbird. Journal of Avian Biology 48: technical support and tags; and the USGS Bird Banding Lab 209–219. and the Canadian Wildlife Service for their support. For field Cormier, R. L., D. L. Humple, T. Gardali, and N. E. Seavy (2013). assistance in British Columbia we thank Rick Schortinghuis, Light-level geolocators reveal strong migratory connectivity Marianne Dawson, Christian Kelly, Stacey Hrushowy, Daniel and within winter movements for a coastal California Donnecke, and Eric Demers. For field support in California we Swainson’s Thrush population. The Auk 130:283–290. thank Palomarin Field Station interns and staff, especially Dawson, W. L. (1909). The Birds of Washington. Occidental Mark Dettling. We thank Bridget Stutchbury for supplying the Publishing, Seattle, WA, USA. light-level geolocators deployed at the Vancouver Island study DeLuca, W. V., B. K. Woodworth, C. C. Rimmer, P. P. Marra, P. D. area. We are grateful to Point Reyes National Seashore, Marin Taylor, K. P. McFarland, S. A. Mackenzie, and D. R. Norris County Open Space District, and numerous private landown- (2015). Transoceanic migration by a 12 g songbird. Biology ers for their cooperation and support of our research. Letters 11(4):20141045. Funding statement: We thank the University of Manitoba, Hill, R. D., and M. J. Braun (2001). Geolocation by light level. In the March Conservation Fund for support of this migratory Electronic Tagging and Tracking in Marine Fisheries (J. R. connectivity study at Palomarin, and are also grateful to the SibertandJ.L.Nielsen,Editors).Springer,Dordrecht, Netherlands. pp. 315–330. Kimball Foundation, the Karen A. and Kevin W. Kennedy Lisovski, S., and S. Hahn (2013). GeoLight-processing and Foundation, the Makray Foundation, Marcia Grand, an analysing light-based geolocation in R. Methods in Ecology anonymous donor, and the members and board of directors and Evolution 3:1055–1059. of Point Blue Conservation Science for their support of Lisovski, S., C. M. Hewson, R. H. G. Klaassen, F. Korner-Nievergelt, Palomarin. M. W. Kristensen, and S. Hahn (2012). Geolocation by light: Ethics statement: This study was conducted in accordance Accuracy and precision affected by environmental factors. with the recommendations of the Ornithological Council’s Methods in Ecology and Evolution 3:603–612. Guidelines to the Use of Wild Birds in Research and was McKinnon, E. A., C. Artuso, and O. P. Love (2017). The mystery of approved by the York University Animal Care Committee the missing warbler. Ecology 98:1970–1972. (2009-2 W (R1)). McKinnon, E. A., K. C. Fraser, and B. J. M. Stutchbury (2013). New Author contributions: K.C.F., M.S., and B.F.C. conceived the discoveries in landbird migration using geolocators, and a idea, design, and experiment. B.F.C., M.S., A.N., R.L.C., and flight plan for the future. The Auk 130:211–222. D.L.H. performed the experiments (collected data, conducted McKinnon, E. A., C. Q. Stanley, and B. J. M. Stutchbury (2015). the research). K.C.F., A.R.C., B.F.C., M.S., A.N., A.C.S., R.L.C., Carry-over effects of nonbreeding habitat on start-to-finish and D.L.H. wrote the paper. K.C.F., A.R.C., B.F.C., and M.S. spring migration performance of a songbird. PLOS One developed or designed the methods. A.R.C., B.F.C., A.S., and 10(11):e0141580. K.C.F. analyzed the data. Nelson, A. R., R. L. Cormier, D. L. Humple, R. Sehgal, and N. E. Data depository: Data will be deposited at Movebank. Seavy (2016). Migration patterns of San Francisco Bay Area Hermit Thrushes differ across a fine spatial scale. Animal Migration 3:1–13. LITERATURE CITED Newton, I. (2008). The Migration Ecology of Birds. Academic Alcock, A. (2009). Animal Behavior, 9th ed. Sinauer Associates, Press, London, UK. Sunderland, MA, USA. Pyle, P., and S. N. G. Howell (1997). Identification Guide to North Alerstam, T., and A. Hedenstrom (1998). The development of American Birds, Part 1: Columbidae to Ploceidae. Slate Creek bird migration theory. Journal of Avian Biology 29:343–369. Press, Bolinas, CA, USA. Ambrosini, R., A. P. Møller, and N. Saino (2009). A quantitative R Core Team (2017). R: A Language and Environment for measure of migratory connectivity. Journal of Theoretical Statistical Computing. R Foundation for Statistical Comput- Biology 257:203–211. ing, Vienna, Austria. American Ornithologists’ Union (1998). Check-list of North Ramos, R., V. Sanz, T. Militao, J. Bried, V. C. Neves, M. Biscoito, R. American Birds. American Ornithologists’ Union, Washington, A. Phillips, F. Zino, and J. Gonzalez-Solis (2015). Leapfrog DC, USA. migration and habitat preferences of a small oceanic seabird, Bell, C. P. (1997). Leap-frog migration in the Fox Sparrow: Bulwer’s petrel (Bulweria bulwerii). Journal of Biogeography Minimizing the cost of spring migration. The Condor 99:470– 42:1651–1664. 477. Rappole, J. H., and A. R. Tipton (1991). New harness design for Bearhop, S., W. Fiedler, R. W. Furness, S. C. Votier, S. 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APPENDIX TABLE 1. Geolocator and GPS deployment and retrieval locations. Trapped - Observed - Latitude Longitude Geolocators/ Geolocators/ geolocator not Location (8N) (8W) GPS deployed GPS retrieved missing trapped

Vancouver Island, British Columbia Central Saanich 48.57 123.46 1 0 48.59 123.42 1 0 1 48.58 123.41 0 0 Hector Road 48.48 123.42 1 1 48.49 123.43 3 2 48.49 123.43 1 0 1 48.48 123.43 2 0 Oldfield 48.55 123.41 1 0 1 48.55 123.41 6 0 1 48.55 123.41 3 2 48.55 123.42 0 0 Cordova/Gordon Head 48.51 123.36 0 0 48.50 123.37 3 1 48.47 123.31 11 1 48.47 123.34 0 1 48.47 123.34 1 0 1 Saanich 48.46 123.37 0 0 Metchosin 48.34 123.57 0 0 Colwood 48.43 123.47 1 0 Victoria subtotals 26 7 3 3 N. Nanaimo 49.23 124.00 3 2 0 0 49.23 123.98 1 1 Nanaimo subtotals 4 3 0 0 Totals 30 10 3 3

Point Reyes, California Palomarin Field Station 37.93 122.74 9/6 0/0 Pine Gulch Creek 37.92 122.69 15/2 3/1 Private Property 37.90 122.70 0/7 0/4 (2 had no data) Totals 24/8 3/5

The Auk: Ornithological Advances 135:572–582, Q 2018 American Ornithological Society K. C. Fraser, A. Roberto-Charron, B. Cousens, et al. No leapfrog migration in Sooty Fox Sparrow 581

APPENDIX FIGURE 3. The leapfrog migration system of Sooty Fox Sparrow as proposed by Swarth (1920) and elaborated by Bell (1997). Numbers represent subspecies: 1 ¼ Passerella iliaca unalaschcensis,2¼ P. i. insularis,3¼ P. i. sinuosa,4¼ P. i. annectens,5¼ P. i. townsendi, and 6 ¼ P. i. fuliginosa, predicted to be resident/sedentary. Colors show overwintering regions and connections to breeding areas (by dashed lines), where groups were predicted be migratory.

The Auk: Ornithological Advances 135:572–582, Q 2018 American Ornithological Society 582 No leapfrog migration in Sooty Fox Sparrow K. C. Fraser, A. Roberto-Charron, B. Cousens, et al.

APPENDIX FIGURE 4. Breeding site location estimates based upon geolocator deployments at (A) Victoria, British Columbia, (B) Nanaimo, British Columbia, (C) Point Reyes, California, and (D) GPS deployments at Point Reyes, California.

The Auk: Ornithological Advances 135:572–582, Q 2018 American Ornithological Society